T2 dependence of the resistivity in the Cu-O chains of YBa2Cu3O6.9

Abstract

The temperature dependence of the electrical resistivity along the a and b axes of ${\mathrm{YBa}}_2$ ${\mathrm{Cu}}_3$ ${\mathrm{O}}_{6.9}$ has been measured in high-purity fully detwinned single crystals. Below 300 K, ${\mathrm{\rho }}_{\mathit{a}}$(T) was found to be perfectly linear, while ${\mathrm{\rho }}_{\mathit{b}}$(T) revealed a distinct upward curvature. Viewing the b-axis conductivity as the sum of conductivities in the ${\mathrm{CuO}}_2$ planes and along the Cu-O chains, a ${\mathit{T}}^2$ dependence for the chain resistivity is obtained. Such a dependence, also found in quasi-one-dimensional conductors, explains a number of hitherto ill-identified deviations from linearity reported recently.